How do you make sure the thing you are hoping saves everyone has an inclination (or ability) to do so? How do you make sure it is only afflicted with the human parts you like and not the ones you don't?

Nothing can save everyone, that's the point. There is no miracle out there that suddenly makes the world a fairy tale. And I don't have an answer, otherwise I would have made a claim to that effect.

This is a hard problem, and the human mind is not naturally equipped to work at the scales in question. Perhaps the solution is a thing (e.g a program), a process like democracy of some ilk, or something else entirely. The important part is recognizing our limits and working to account for them in our solutions. Acting without that awareness is a recipe for disaster.